This invention relates to alternate refrigerant automotive air conditioning systems in general, and specifically to such a system that has a means for selectively segregating the refrigerant within independent and isolated loops.
Currently used automotive air conditioning system refrigerants may, in the future, be eliminated in favor of refrigerants with less perceived global warming potential. Depending on the alternate refrigerant used, it may be desirable to provide various systems and mechanisms to isolate and segregate the alternate refrigerant with the air conditioning system, or to block it from reaching certain parts of the vehicle under certain conditions, such as a system leak. The same considerations may apply to residential systems.
Current proposals for such mechanisms typically incorporate nothing more than the obvious expedient of shut off or blocking valves designed to close off various points along the refrigeration lines in the event of leaks or breaks, similar to automatically closing bulkhead doors in a ship. Blocking valves, operated by solenoids, may close automatically when a compressor is shut down, or in the event of a sensed collision or in the event of a sensed leak. Examples of these various proposals may be seen in U.S. Pat. Nos. 5,660,051, 5,918,475 and 5,983,657. To the extent that these designs create an automatic blockage of the refrigerant lines between the exterior mounted condenser and the interior mounted evaporator, the valves, two of which are needed (one on either side of the evaporator) have to reliably seal a high-pressure area (condenser) from a low-pressure area (evaporator). Since seals is such an application are required, at least initially, to hold back a high pressure, they are therefore subject to leakage, as is any high-pressure seal.
The subject invention provides a single valve mechanism that isolates the low pressure area of the refrigerant system from the high pressure area without the necessity of holding back a high pressure, as with a conventional blocking valve.
In the preferred embodiment disclosed, an air conditioning system has a low pressure area in the form of an evaporator with an inlet and an outlet, a compressor with an inlet located downstream of the evaporator, and a high pressure area in the form of a condenser with an inlet located downstream of the compressor and an outlet located upstream of the evaporator inlet. This is typical of automotive and other air conditioning systems. It may be desirable to limit the amount of refrigerant that is in, and which can continue to enter, the lower pressure evaporator after the compressor and system have been shut down for any reason.
In the preferred embodiment disclosed, a valve housing has several possible refrigerant ports. On one side of the valve housing, there are three ports, upper, central and lower. The upper port is connected to the condenser outlet and always receives refrigerant therefrom, regardless of its ultimate destination. The central port is connected to the compressor inlet (or compressor suction port), and always directs refrigerant thereto, regardless of its immediate source. The lower port is connected to the evaporator outlet, and a single port on the opposite side of the valve housing is connected to the evaporator inlet. Inside the valve housing, a suitable mechanism, movable between a normal operating position and an evaporator isolation position, serves to selectively interconnect or block the various ports from one another. In the operating position, selected when the compressor is running and all other sensed conditions are normal, the valve mechanism moves so that the upper port and single port of the housing are interconnected, while the central and lower ports are interconnected. This allows refrigerant to flow from the compressor and high pressure condenser into the upper port, out the single port and into the evaporator inlet, through the evaporator to the lower port, and then out the central port to the compressor inlet. This single loop is typical of the standard cycle. In the evaporator isolation position, selected when the compressor is shut off and/or other abnormal conditions (leakage) are sensed, the valve mechanism moves so that the upper and central ports are interconnected, while the single and lower ports are interconnected. This puts the evaporator in its own isolated loop, with its inlet and outlet by passed or short circuited one to the other. At the same time, the compressor, high pressure condenser and any other components associated therewith are placed in a separate, isolated loop, around which refrigerant can flow until pressure is equalized within that loop. At no point is a location within a loop simply sealed or blocked, in dam like fashion. While the two loops have to be kept substantially sealed from one another, the pressure differential between them is not as high as the pressure differential would be across a standard shut off valve, and the necessary sealing integrity is easily achieved by a close fit of the single valve mechanism within the single valve housing.